December 2020 Observations and Discussion

[bud2380]

Euro hits a brick wall with snow totals in Iowa just to the west of Iowa city and Cedar Rapids. 

[Grizzcoat]

Got get the "L" East of your longitude and your golden -and of course S

[The Snowman]

0z ECMWF total snow through Hour 162. Kinda funky in both the shape of the highest totals and how it handles that second low pressure system after the main one passes thru (from Hour 150 onwards)

[Grizzcoat]

Still not true arctic air behind this thing. That is concerning not only here in C.IA , but also for those E .

[bud2380]

Wouldn’t take much of a dip SE to get eastern Iowa in that heavy snow band. This storm is still a long ways out.  I have plenty to be excited and concerned about. Seems I always ride the edge of the heavy snow/rain with these. 

[Hawkeye]

Once again, when the early-week system exits to the east a big ridge blows up ahead of the big system, all the way up into Canada.  It's like a big wall.  This is not a look many of us want to see.

[Grizzcoat]

The more this things gets held up - meanders or even tries to retrograde - by the ridge , the more it's likely to find the temp gradient and snowpack / nonsnowpack area and track just along it. The system late weekend will have a say in this. Regardless- the L is almost certain to track somewhere through IA. They always do .

[Tom]

55 minutes ago, Grizzcoat said:

The more this things gets held up - meanders or even tries to retrograde - by the ridge , the more it's likely to find the temp gradient and snowpack / nonsnowpack area and track just along it. The system late weekend will have a say in this. Regardless- the L is almost certain to track somewhere through IA. They always do .

That'll be the key to the ultimate track of this system.  The problem I see for those of us farther east is the arctic HP following the late weekend system drives to much far south and east which then deflects the storm to cut NW.  We either need that HP to press less farther south or need the models to pick up on more HP in southern Canada in future runs.

00z GEFS show this pretty clearly...what is really odd is the fact that all the teleconnections DO NOT support a NW cutter.  I'm baffled by this because the ONE time we have a massive storm showing up and the teleconnections all support a track farther south, the models take it NW...uggg!!!  I mean, the PNA is (+), -AO/-NAO and neutral EPO...what the freak!

 

 

[Tom]

This one has the central Plains up into MN/N WI written all over it...my goodness, what a treat you guys to the west of here are gearing up towards.  To see a 12" mean for parts of KS/NE/IA 5+ days out is incredible.  #BuildTheGlacier

 

 

 

[Tom]

00z Euro Control...

[Tom]

06z GFS...NW trends continue...

 

[GDR]

You can guarantee that the low tracks further nw in Iowa. Look for a big shift nw in the coming days.

[GDR]

[Grizzcoat]

It should be mentioned that said storm - instead of taking an Eastern Route and giving many on this thread a nice snowstorm - could easily ride up the edge of the snowpack on the WEST  side. There is a tremendous lack of snow cover for end of DEC in Dakotas and E MT and E.WY. Likely? Probably not. But remember the trends - the strong ridge along the E.Coast and lack of true Arctic air behind it ( this is the big one for me- as no strong "H" to the NW to block this from happening)  are clues that this thought have at least some merit. IF so- would be rain or dry slot for most.  need the weekend system to lay down some snow in W parts and bring more chill than models are showing (long shot). Still said event is 5+ days away -- anything can happen.

[CentralNebWeather]

NWS Hastings morning disco. 
 

Attention then turns toward middle of next week as both deterministic and ensemble guidance (from both EC/EPS and GFS/GEFS) continue to show at least the potential for a significant cyclone somewhere in the central Plains. Obviously, confidence on details such as exact timing, track, and pcpn amounts remains too low to discuss this far out...but there are several things that have caught my attention that gives me reasonable confidence this system will sure be one to watch:

- Run to run and model to model consistency between GEFS and EPS. Both ensemble means given warning level snow to at least parts of the CWA, and both have done this for at least a few runs now. 

Most of the ensemble members that don`t give specifically our CWA much pcpn, still have a significant system nearby, just not over us. Certainly not usual to have track diffs this far out. - Appears the Gulf of Mexico will be wide open for moisture - Strong indications that the primary upper low will slow down, become negatively tilted, and eventually close off - System will probably have pre-existing cold air to work with -

Organized low to mid level low pressure could result in strong winds (but not necessarily stronger than most recent system) Obviously, still plenty of time for model fluctuations and to work out additional details. Seems only fitting for 2020 to go out with a mess of a winter storm. It`s advised that folks with weather sensitive interests next week stay up to date with latest forecasts from trusted sources, and not get caught up in the hype of specific high end snow amounts this far out.

 

[clintbeed1993]

11 minutes ago, Grizzcoat said:

It should be mentioned that said storm - instead of taking an Eastern Route and giving many on this thread a nice snowstorm - could easily ride up the edge of the snowpack on the WEST  side. There is a tremendous lack of snow cover for end of DEC in Dakotas and E MT and E.WY. Likely? Probably not. But remember the trends - the strong ridge on the East and lack of true Arctic air behind it are clues that this thought has at least some merit. IF so- would be rain or dry slot for most.

 

Tanking AO and NAO SHOULD prevent that imho. It'll cut, but not that hard

[Grizzcoat]

Hey Clinton- can you post 06Z EURO maps?  Thanks. ( all I got is out 90 hours)

[westMJim]

Yesterdays official high of 53 (I had a high of 54 here at my house) was the 3rd warmest day of record at Grand Rapids for any December 23rd The high tied 1979 and 1957 for 3rd place. The record high of 60 was recorded in 2015 and in 2nd place is a high of 57 set 1982 and 1941. There was around a 0.25” of rain fall late yesterday and overnight. Currently light snow if falling but so far just a dusting here at my house. The current temperature is 22.

[Clinton]

5 minutes ago, Grizzcoat said:

Hey Clinton- can you post 06Z EURO maps?  Thanks. ( all I got is out 90 hours)

Yes I can.  EC is getting ready to go right now.  

[bud2380]

We’re not even in range of the NAM yet, not even close actually. The blizzard that hit yesterday was projected by the Euro and others to drop a few inches in eastern Iowa only 72 hours away from the storm before it shifted massively NW and stronger. The storm before that that brought several inches to Iowa was showing a foot for North Dakota and Northern MN before shifting hundreds of miles south. So more changes, potentially significant are in store. I just hope the changes are to shift further south or a more west to east track instead of the cutter we are seeing now. 

[Clinton]

34 minutes ago, Grizzcoat said:

Hey Clinton- can you post 06Z EURO maps?  Thanks. ( all I got is out 90 hours)

6z EC only goes to hr 144

 

[St Paul Storm]

The ridge to the east needs to be overcome if this thing is going to go south. You can talk about the low following the snowpack line, but it’s importance is fairly minimal in comparison to whether or not that ridge can break down. 

[Stormy]

My office (DVN) in the latest disco agrees with Tom’s expectations.

Monday through Thursday (the last week of 2020!): It appears that
the deep storm system that brought the big blizzard to nw IA and 
MN yesterday has buckled the weather pattern into La Nina for the 
remainder of the winter. This is your heads-up that a more active 
(snowier and colder) regime is in the offing for the Midwest. Next
up will be another powerful trough that will come out of the 
eastern Pacific early in the week, then track through the southern
Rockies and into the Midwest by the middle of the week. There is 
high confidence of an intense storm system impacting the Midwest 
in the Tuesday through Thursday time frame. There is the potential
for plowable snow, freezing rain or even plain rain depending on 
the exact track and unfortunately too far out there yet for 
details on who gets what. Stay tuned! Haase

 

[St Paul Storm]

Impossible to measure, but I’ll go with around 7-8” from yesterday’s storm. Sunrise this morning was amazing. 
 

Merry Christmas to you all! 

[Clinton]

My office has it narrowed down lol, storm between the I 44 corridor and I 90

The pattern will shift quickly on Christmas afternoon as
ridging and southerly flow return to the region. This will create a
sharp temperature gradient of 40s along the KS/Mo border with 20s
over NE Missouri. This warming trend will continue into Saturday as
a warm front develops over our area with highs in the 50s. This low
pressure system will slowly shift east with the cold front coming
through Sunday afternoon. Currently this system looks relatively dry
with no real PoPs expected. Once winds shift to the NW the cooler
airmass will build into the area, dropping lows into the teens to
20s Monday morning. Wind chills will also be an issue with 10kts of
wind or so in the morning, bringing values down to the single digits
to teens. This cooler airmass will stay in place through Tuesday.
How far south this cooler airmass goes will become a major factor in
how a possible winter storm Tuesday will play out. Current ensembles
and our NBM model have the freezing line right down by Springfield
Tuesday morning and plenty of cold air in place as the warm front of
the system would push into the area. The current NBM has the 50th
percentile for snowfall around 3-4" north of the Missouri River and
1-2" to the south. We`d have to tap into the 75-90th percentiles to
get to winter storm criteria for snow. The deterministic models are
depicting a synoptic setup with warmer air aloft getting into our
area, increasing the possibility of freezing rain or sleet being an
issue. The 50th percentile for total ice is around 0.01-0.05", but
the 90th percentiles jump up to more like 0.1 over the area. It is
still way to far out to clamp on to any real numbers, but the signal
for a nice winter storm system moving through from I-44 to I-90 is
looking more likely and worth watching trends as we get closer.

---

 

[Stormy]

I’m needing to decide if I still want to make the trip to eastern TN starting early on the morning of the 31st. As of now it looks like precipitation will hopefully just be winding down at that time. Or are you guys seeing something different? And what about the first 3 or so days of January? If I was seeing right the CMC is showing a potential weaker system.

[westMJim]

Getting moderate to at times heavy snow fall here now. The ground is now covered and it looks like there is now at least 1” of snow on the ground. The current temperature here is now down to 21

[mlgamer]

29 minutes ago, Clinton said:

6z EC only goes to hr 144

 

SLP tracking through northeast KS...I've only seen that about a million times over the past 25 yrs.

[Clinton]

2 minutes ago, Sparky said:

I’m needing to decide if I still want to make the trip to eastern TN starting early on the morning of the 31st. As of now it looks like precipitation will hopefully just be winding down at that time. Or are you guys seeing something different? And what about the first 3 or so days of January? If I was seeing right the CMC is showing a potential weaker system.

CMC and Euro control have a weaker system.  There should be one around the 2nd or 3rd.

[Clinton]

2 minutes ago, mlgamer said:

SLP tracking through northeast KS...I've only seen that about a million times over the past 25 yrs.

We need the high around the GL to be stronger.

[FarmerRick]

Quote

 

Jim Flowers

ciSt1Slponsoi redhr  · 

 

The key to the forecast next week is not the big trof from nebraska south but a small short wave in eastern Idaho that is preventing the ridge from building behind the nebraska trof. It has trended stronger with neb trof weaker and upper low much farther north. As a result precip amounts have been cut in half by euro. Low has shifted from Tx to sw neb on euro. Still produces a lot of snow but not the 20+ amounts hyped in the media.

 

[tStacsh]

31 minutes ago, westMJim said:

Getting moderate to at times heavy snow fall here now. The ground is now covered and it looks like there is now at least 1” of snow on the ground. The current temperature here is now down to 21

I’m under the WSW oriented streamer coming off the lake through GR.   Solid fluffy flakes.  Adding up 1.5” so far.  

[bud2380]

Korean model!

 

[bud2380]

Based on the GFS timing of the storm, we have 5 or 6 more runs of the NAM before the storm will even begin coming into view on the NAM with the SLP forming in CO and precip breaking out in front of it.  It'll be 2 or 3 more days at least before models start honing in on this one.  We should probably start a thread though, so I'll go ahead and do that. 

[St Paul Storm]

Currently -3F with a chill of -27F. We’re going to struggle to get to 0F today with the fresh snowpack. 47F temp change from 24 hours ago. 

[The Snowman]

Parallel ECMWF is northwest compared with the operational

[Grizzcoat]

GFS continues up up and AWAY. 

[Stormy]

Big temp changes for eastern Iowa!

https://mobile.twitter.com/nstewcbs2/status/1342098881484566531

[Niko]

It definitely got colder, but, nothing extreme. Temp at 27F under mostly cloudy skies.

[Niko]

This pattern looks like a Nino. December not looking too promising for some. 1 month down, 2 to go.